And coins bought in coinexchange. How are you gonna convert those to the new coin. I don't see the point if the coin supply remains the same.
This is the 1000 dollar question. Are exchange users who bought the coins gonna be fucked or will there just be a coin swap on the website?
If you are asking me, the best option would be to offer a SWAP. So all the investors can take their BTBc coins, independently whether they are on the platform, wallet or exchange, and convert them into the respective new currency.
The only question that remains is what he is gonna achieve with this swap. He can adjust miner difficulty at any time in order to stop the exploitation. Except he has discovered a security flaw in his blockchain (so he is hard forking).